Self-orienting radio direction finder



Empf/6) TING RADIO DIRECTION FINDER w. L.. CARLSON Erm.

SELF-ORIEN Filed Maron 19, 1958 Get. I 7, I 944;

fom TA B 1 E cross/Ep .5H/mofa f .40ansV CALE Patented oct. 11, 1944 2,360,810

SELF-'ORIENTING RADIO DIRECTION FINDER Wendell L. Carlson, Haddonfeld, N. J., and Donald S. Bond, Philadelphia, Pa., assignors to Radio Corporation of America, a corporation UNiTsD of Delaware Application March 19, 1938, Serial No. 196,816

11 Claims. `(Cl. Z50- 11) Our invention relates to radio direction finders and more specifically to radio direction finders in which directive antennas are self-oriented.

We are aware that self-orienting directive anradio frequency transformer is connected to a radio frequency amplifier tube V1. The output of the radio frequency tube V1 is connected to the primary of the radio frequency transformer tennas have been used in connection with radio 5 5 The secondary 1 of the radio frequency receivers for direction finding. In some instaltransformer 5 is preferably tuned to resonance lations, signals from the directive antenna are by a variable capacitor 9. The secondary circombined with signals from a nondirective ancuit l, 9 is connected to a radio receiver I I which tenna, whereby a cardioid pattern may be obmay include a radio frequency amplifier, detectained. If the cardioid pattern is used, no am- 10 tor-oscillator, intermediate frequency amplifier, biguity is present because the directive antenna second detector, automatic sensitivity control, is oriented atthe proper one of its null positions and audio frequency amplifier. Inasmuch as the to indicate the direction of the transmitting radio receiver per se is not our invention and is station from which signals are being received, well known to those skilled in the art, no dei. e., the Wave front of the signal waves. Since tailed description of the CilCJlS S neCeSSarysuch devices are operated at a point of minimum The output from the audio stages of the radio response, we have found that, because of the receiver is connected through a band pass filter inability to shield the nondirective antenna, such to a transformer I3. The audio output circuit systems tend to be unreliable in the presence of may be connected to telephone receivers, which rain static. In order that a self-orienting diare used for communication purposes. rection finder may be used during the presence Loop 2 is angularly disposed with respect to of rain static, we have found it expedient to loop I. Both loops I and 2 are shielded and are use crossed shielded loop antennas which are rotatable together by means of a common shaft comparatively free of undesired response from which is connected to a motor hereinafter derain static. While self-orienting, crossed loops scribed. It should be understood that the loop will have 180 ambiguity; this is preferable to terminals may be Connected through slip rings having no directive indication whatsoever, or and brushes not shown. The terminals of the manually operating a directive loop. second loop are connected to the primary of a It is one of the objects of our invention to radio frequency transformer I5. One terminal provide means in a direction finder whereby of the secondary of this transformer is grounded. self-orienting loops are used to indicate direc- The other terminal is connected through capacition. Another object of our invention is to protors I'I, I9 to the respective control grids of the vide means in a self-orienting or left-right thermionic tubes V2 and V3, which are connected direction finder whereby the device will operate to function as a balanced modulator. The anode in the presence of rain static. Another object circuits of tubes V2 and V3 are connected in pushof our invention is to provide means whereby a pull relation to a primary Winding 2l which is reversible motor operates to orient a pair of coupled to the secondary I of the radio frecrossed loops to indicate the wave front of refluency transformer 5. The mid-point of the ceived signals. A further object is to provide primary winding 2l is connected to B+. crossed loops whereby one loop is operating at 40 The control grids of the balanced modulator its null position when the other. loop is operating tubes V2 and V3 are also connected through irnat or near its maximum and in which the lat- Dedances 23, 25 to the secondary 21 0f an audO ter loop may be used to receive communication frequency tTanSfOlmel 29- The SeCOIldary Windsignals simultaneously with the self-orientation ing 2T iS gl'OuIlded at tS mid-130mb The prof the loops. mary Winding of the audio frequency transu In describing the invention, reference will be former is Connected to an A.C. generator 3l made to the accompanying drawing in which or any suitable source of audio frequency cur- Figure 1 is a schematic circuit diagram of rent. The A.C. is also connected through a one embodiment of the invention; and phase shifter 33 to a field winding 35 of a two- Figures 2a, 2b and 2c are response patterns 50 phase motor 31. The other field winding 39 which are used to illustrate the theory of operaof the motor is connected to the output of the tion, audio frequency amplifier by means of the au- Referring to Fig. l, a shielded loop antenna, dio frequency transformer I3. The rotor of the I is connected to the primary of the radio fretwo-phase motor is coupled to the rotatable shaft quency transformer 3. 'Ihe secondary of the of the loops I and 2.

The coupling 36 between the motor 31 and the loops Nos. I and 2 preferably includes a pointer member 38 and a scale 40.

The operation of the foregoing circuit is as follows: Radio frequency currents induced in loop No. I are amplified by the tube V1 and provide a carrier frequency :which is-applied to the radio receiver II. Radio frequency'v currents induced in loop No. 2 are applied to the modulators V2, V3 but since these tubes are connected in push-pull relation and are balanced, the carrier frequency currents are eliminated. I-Iow-` ever, the audio frequency currents applied from the A.-C. generator 3| alternately fkey-on, one of the tubes V2 and key-off the othertube, thus modulating the signal currents induced-in loop No. 2 and providing currents of sideband frequencies, which are also applied to the radio receiver. Y

The pattern of loop No. I will be a figure 8, Such as shown by yS in Fig. 2a. The pattern of loop No. 2 is also a gure 8, Yas indicated by T. When the modulator tube V2 is operating, the phases of the currents in the two'loops (each having a figure 8 response characteristic) combine to form a directive pattern X. When the tube V3 is operating, the resultant pattern Y is shown in Fig. 2b. Since the resultant patterns X and Y alternately appear at the frequency of the A.C. source 3|, these resultant patterns will appear as shown in Fig. 2c. v. It will be seen that the pattern X represents currents which tend to rotate the motor 31 in a clockwise direction, while the currents represented by Y tend to rotate the motor in a counter-clockwise direction.

If loop No. I is oriented along the line O-180, Y

and provided the signal originates along this line, the effects of the currents representedr by X and Y will be equal and opposite so that the rotor of the motor 31 will be stationary. If the loop No. I is oriented at any other position excepting 90-270, and provided the signal originates along the line.0180, the currents represented by X and Y will be unequal and therefore their resultant will operate the rotor ofthe motor 3l in s uch a direction as to approach-the nearer of the two points 0-180. If, however, the loop No.'I lies along the line. 90-270, and assuming that the signal is arriving from a direction corresponding to the line 0-l80, no carrier frequency currents from loop No. I will be present and, therefore, an equilibrium position will be found which, however, will be unstable. A slight transient current will be sufficient to unbalance the vresultant currents in one direction or the other such that the rotor will revolve until loop No. I is driven to the position 0`180, the pointer which corresponds in position to loop No. I will indicate the direction from which the signals areY being received. Thus, if loop No. I assumes any position other than 0-180, the currents in the field winding 39 will not be zero and will be of such phase that rotation will take place'until the current becomes zero.

Thus, the invention has been described as a pair of rotatable crossed shielded loops which are connected to the rotor of a reversible motor. The signals from vone of the loopsv provide carrier frequency currents. The signals from the other loop are applied to a pair of tubes connected in balanced relation and arranged for alternate operation. The keying or modulation frequency currents appear in the radio receiver output as able means.

an audio frequency current whose amplitude varies and whose phase reverses as a function of the loop position. The output current of reversible phase and a current of fixed phase are applied to a two-phase motor which is suitably coupled toV the loops, to thereby rotate the loops until the reversible phase current becomes substantially zero.

While we have shown loop antennas arranged to cross each other at right angles, other angular disposition of the 'loops may be used. Likewise, any directive antenna may be used in place of the loops, For example, a dipole is an equivalent of a loop in its directive pattern. In some installations, such as an aircraft, the directive antennas may be` Xedly mounted on the craft, and the motor used to orient the craft Yby suit- If the system is used for communication purposes, the directive antenna receiving the carrier currents, which will include the signalling currents, will automatically have a maximum response because the otherV directive antenna will bey oriented to have alminimum response, and. therefore communication will beat maximum response and directional indicationmost sharply defined at the same time. Furthermore, this condition of effective communication response and directive indication will be continuously maintained.

n We claim as our invention: 1. A direction finder including, in combination, a pair of crossed loops, means connecting one of said loops to a radio frequency amplifier, means connecting the other of said loops to a balanced modulator, an audioV frequency current source, means for applying an audio frequency current from said source to said balanced modulator, a radio receiver, means coupling said radio frequency. amplifier and said balanced modulator output to said receiver, a two-phase motor, said motor being operated by currents of said source and by the'output currents ofsaid receiver, and means coupling said loops to said motor whereby the loops are oriented byf said motor until the output currents become substantially zero. 2. A direction nder including, in Y combination, a pair of crossed loops, means for effectively shielding each .of said-loops from rain static,

means connecting one of said loops'to a radio fre-V quency amplifier, means connecting the other of said loops to a balanced modulator, an audio frequency current source, means for applying an audio frequency current from said sourceto said balanced modulator, a radio receiver, means coupling said radio frequency amplifier and said balancedmodulator output to said receiver,- a twophase motor, said motor beingoperated by currents of said source and by the output `currents ofasaid receiver, and means coupling said loops to said motor whereby the loops are oriented vby said motor until the output currents become substantially zero.

. 3. In a radio direction finder, the combination of a pair of directive antennas, said antennas arranged for rotation, a radio receiving device, means for applying signal currents induced in one of said antennas Ato said receiving device,

- a source-of audio frequency current, means for modulating currents derived from said other an-V tenna with currents from said source, means for applying said modulatedV currents to said receiving device, a two-phase motor including a rotor, Ymeans for applying currents of one phase derived from' said source and of another phase derivedfromsaid receiving device to saidmotor,

and means coupling said rotor and said directive antennas.

4. In a radio direction finder, a pair of antennas each having figure 8 response patterns angularly disposed with respect to each other, a radio receiver including an audio output circuit, means coupling one antenna to said receiver', a balanced modulator, means including said modulator for coupling said other antenna to said receiver, an audio frequency current source,

means for applying said audio frequency current to said modulator, a two-phase motor including a rotor, means for applying currents derived from said source and said output circuit to said motor, and means coupling said rotor and said antennas whereby the antennas are rotated as a function of the received signals.

5. In a device of the character of claim 4, means for shielding said antennas.

6. In a radio direction finder including a pair of directive antennas, a source of radio signals and a two phase motor, the method of orienting said antennas by means of said two-phase motor which comprises deriving carrier frequency currents from one of said antennas, deriving communication signals from said antenna, deriving currents of side band frequency from the other of said antennas by applying currents of modulation frequency and by eliminating the currents of carrier frequency, combining said firstmentioned carrier frequency currents and said side band frequency currents, deriving an audio output current from said combined currents, aprplying said audio output and said modulation currents to said two-phase motor to move its rotor as a function of the phase of the received currents, and orienting said antennas by the operation of said motor until the audio output current becomes substantially zero and said communication signals derived from said first-mentioned antenna reach a maximum, and utilizing said communication signals.

7. In a, radio direction finder including a pair of directive antennas, a source of radio signals, and a reversible motor, the method of orienting said antennas by means of said reversible motor which comprises deriving carrier frequency currents from one of said antennas deriving communication signals from said antenna, deriving currents of side band frequency from the other on said antennas by applying currents of modulation frequency and by eliminating the currents of carrier frequency, combining said first-mentioned carrier frequency currents and said side band frequency currents, deriving an audio output current from said combined currents, applying said audio output and said modulation currents to said reversible motor to move its rotor as a function of the phase of the received currents, and orienting said antennas by the operation of said motor until the audio output current becomes substantially zero and said communication signals derived from said first-mentioned antenna reach a maximum, and utilizing said communication signals.

8. In a radio direction nder including an indicator, the method of determining direction which comprises deriving a current of carrier frequency from a signal wave Whose wave front is to be determined, deriving communication signals from said Wave, deriving a second carrier current, modulating said second carrier current by a modulation current, eliminating said second carrier current, deriving currents of side band frequency from said modulated currents, combining said currents of side band frequency and said first-mentioned carrier currents, obtaining from said combined currents a modulating frequency current, deriving forces from said rst-mentioned modulation current and said second-mentioned modulating frequency current, and applying said forces to produce rotation of said indicator until the second of said modulating currents becomes substantially zero and said communication signals reach a maximum so that said Wave front is indicated by the cessation of said rotation and utilizing said communication signals.

V9. In a radio direction finder including selforienting crossed directive antennas and a source of radio signals, the method of determining direction which comprises deriving from one antenna a current of carrier frequency from a signal wave Whose wave front is to be determined, deriving communication signals from said antenna, deriving a second carrier current from said second antenna, modulating said second carrier current by a modulation current, eliminating said second carrier current, deriving currents of side band frequency from said modulated currents, combining said currents of side band frequency and said first-mentioned carrier currents, obtaining from said combined currents a current of modulation frequency, deriving forces from said first-mentioned modulation current and said second-mentioned modulation frequency current, and applying said forces to produceV simultaneous rotation of said antennas until the second of said modulating currents becomes substantially zero and said communication signals derived from said first-mentioned antenna reach a maximum whereby said Wave front is indicated by the position of said antennas, and utilizing said communication signals.

10. In a system of the character described, the combination of crossed directive antennas, a source of signals, means including a two-phase motor for self-orienting said antennas to a position in which one of said antennas has a maximum response and the other of said antennas has a minimum response to said signals, communication signal-indicating means coupled to said first-mentioned antenna and means coupling said self-orienting means to both of said antennas so that said antennas may be simultaneously used to indicate the direction of the wave front of received signals when said one antenna is used for communication.

11. In a system of the character described, the combination of a pair of directive antennas having their directive patterns disposed so that the maximum of one substantially coincides with the minimum of the other, means coupling said antennas to a radio receiving device, a signal-indicating instrument connected to said device, means including a two-phase motor coupled to the output of said device and responsive as a function of said directive patterns for rotating said directive antennas to a position in which one of said antennas has a maximum response to communication signals at the same time the other of said 

